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68Ga-Tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid-Glu-[cyclo(Arg-Gly-Asp-D-Phe-Lys)]2.

Authors

Leung K1.

Source

Molecular Imaging and Contrast Agent Database (MICAD) [Internet]. Bethesda (MD): National Center for Biotechnology Information (US); 2004-2013.
2011 Feb 20 [updated 2011 May 12].

Author information

1
National Center for Biotechnology Information, NLM, NIH

Excerpt

Integrins are a family of heterodimeric glycoproteins on cell surfaces that mediate diverse biological events involving cell–cell and cell–matrix interactions (1). Integrins consist of an α and a β subunit and are important for cell adhesion and signal transduction. The αvβ3 integrin is the most prominent receptor affecting tumor growth, tumor invasiveness, metastasis, tumor-induced angiogenesis, inflammation, osteoporosis, and rheumatoid arthritis (2-7). Expression of the αvβ3 integrin is strong on tumor cells and activated endothelial cells, whereas expression is weak on resting endothelial cells and most normal tissues. Antagonists of αvβ3 are being studied as antitumor and antiangiogenic agents, and the agonists of αvβ3 are being studied as angiogenic agents for coronary angiogenesis (6, 8, 9). Extracellular matrix proteins (vitronectin, fibrinogen, laminin, and collagen) contain a tripeptide sequence consisting of Arg-Gly-Asp (RGD), which binds to a variety of integrins, including αvβ3. Various radiolabeled antagonists have been introduced for imaging of tumors and tumor angiogenesis (10). Most cyclic RGD peptides are composed of five amino acids. Haubner et al. (11) reported that various cyclic RGD peptides exhibit selective inhibition of binding to αvβ3 (inhibition concentration (IC50), 7–40 nM) but not to integrins αvβ5 (IC50, 600–4,000 nM) or αIIbβ3 (IC50, 700–5,000 nM). Various radiolabeled cyclic RGD peptides have been found to have high accumulation in tumors in nude mice (12). Janssen et al. (13) reported the development of 111In-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid-Glu-[cyclo(Arg-Gly-Asp-D-Phe-Lys)]2 (111In-DOTA-E-[c(RGDfK)]2) for single-photon emission computed tomography imaging αvβ3 receptors in nude mice bearing ovarian carcinoma tumors. Dijkgraaf et al. (14) also reported the evaluation of 68Ga-DOTA-E-[c(RGDfK)]2 for positron emission tomography (PET) imaging αvβ3 receptors in tumor, which is the topic of this chapter.

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